1. Technical Field
The invention relates to an unhingeable and concealed hinge for switching boxes.
2. Discussion of Prior Art
A hinge is already disclosed in European patent application bearing publishing no. 0 157 344. Similar arrangements are also known from catalogue sheets C 090 and C 100 belonging to the company EMKA Beschlagteile GmbH & Co. KG, Velbert, from March 1985. The latter two designs have the disadvantage that to dismantle the door leaf from the box, the bearing bolt arrangements in the form of angled bolts have to be pulled upwards.
There must always be sufficient space to pull up these bolts and this cannot always be guaranteed. These designs are also disadvantageous in that subsequent assembly of the door leaf is made difficult as the bearing eye for the angled bolt is concealed, therefore hard to find and poorly accessible.
The hinge disclosed in the European patent specification is more advantageous because less space is required for pulling out the bearing bolt in order to dismantle the door--which has to be done occasionally in order to gain better access to the inside of the switching box during wiring. This advantage is due to the bearing bolt being split allowing the removal of each half of the bearing bolt to such an extent that they clear the bearing eye of the first hinge part lying between the U-limbs of the second hinge part. By means of special spring block arrangements the halves of the bearing bolt can also be held in the partially removed position so that subsequent reintroduction of these halves of the bearing bolt is unnecessary when the door leaf is reassembled on the door frame. This is because the ends of the bolt, which are still located in the second hinge part only have to be pressed into the first hinge part.
However, this design also has disadvantages. Two bolts have to be pulled, for which a special tool is required. Also, splitting the bearing bolt or hinge bolt reduces stability, because short bolts tend to tilt. Also, certain difficulties are involved in hanging as prior to inserting the two halves of the bearing bolt, the first and second hinge parts have to be brought into the correct position with regard to one another, in such a way that the bearing eyes of both hinge parts are flush. It has also been shown that as a result of accumulations of paint the bolt can be difficult to operate, so that manual force alone is not enough to push in the bolt, requiring a hammer to be used which can cause damage to the paintwork.
Furthermore, reference is made to catalogue sheets C 085.2 and C085.4, in which hinges are disclosed, on the one hand for individual box applications, and on the other for series box applications in which dismantling also occurs through pulling out an angled bolt, which in the first instance is also the bearing bolt. Both designs are very advantageous for particular applications, but have the disadvantages of requiring space for pulling out the bolt, difficult hanging, particularly when several hinges are attached to a door leaf and have to be simultaneously aligned. This can only succeed with difficulty because there are parts which pivot away which are difficult to manipulate simultaneously. A further disadvantage of the two latter hinges is also that they are visible.